disadvantage of being a copycat

You can only copy what you can see. But, in creative matters, what matters most is the set of choices that were not made and features that did not make it to the final product.

For instance, in math, when you read a proof you need to ask why it is concerned only with the specific class of structures mentioned in the statement. Once you understand the reason why, then you will be able to play with the proof and copy the techniques used in it elsewhere. 

In software product design, what looks like a missing element is often deliberately left out. Inexperienced designers have hard time reverse-engineering the simplicity achieved by their experienced colleagues. That is why they can copy the existing product but never be able to carry it to the next level themselves.